EN
Imperceptivity is understood as expressing the speaker's detachment from the content of the sentence, often through underlining the fact that the speaker was not a witness of the situation spoken about. The semantic structure of imperceptive sentences contains: 1. the semantic component 'says that'; 2. 'speaker's unawareness', which can be noted as 'the speaker does not know whether....'; 3. the necessity of 'the presence of an observer who is not identical with the speaker', whose opinion is the basis of the speech situation, while the speaker shows doubt concerning the truth of the presented content; 4. the possibility functor 'it is possible that'. Examples from Bulgarian, Polish, Ukrainian and English are presented and the peculiarities of the usage of imperceptivity in those languages are discussed.